FIG. 1 shows the frame structure of a Frequency Division Duplex (FDD for short) model in the Long Time Evolution (LTE for short). As shown in FIG. 1, in such a frame structure, a 10 ms radio frame is divided into two half frames, each half frame is partitioned into 10 time slots of 0.5 ms, and two time slots compose a subframe of 1 ms, thus one half frame comprises 5 subframes. When the cyclic prefix is a normal cyclic prefix, one time slot comprises 7 uplink/downlink symbols; when the cyclic prefix is an extended cyclic prefix, one time slot comprises 6 uplink/downlink symbols, and a Second-Synchronization Channel (S-SCH for short) and a Primary-Synchronization Channel (P-SCH for short) are arranged to be transmitted on the last two OFDM symbols of the first time slot. When the cyclic prefix is a normal cyclic prefix, the Physical Broadcast Channel (PBCH for short) is sent on the 4th and 5th OFDM symbols of the first time slot, and the 1st and 2nd OFDM symbols of the second time slot; when the cyclic prefix is an extended cyclic prefix, the physical broadcast channel is sent on the 4th OFDM symbol of the first time slot and the 1st, 2nd, and 3rd OFDM symbols of the second time slot.
FIG. 2 shows the frame structure of the Time Division Duplex (TDD for short) model in the LTE system. As shown in FIG. 2, in such a frame structure, one radio frame of 10 ms is divided into two half frames, each half frame is partitioned into 10 time slots of 0.5 ms, and two time slots compose a subframe of 1 ms, thus one half frame comprises 5 subframes. When the cyclic prefix is a normal cyclic prefix, one time slot comprises 7 uplink/downlink symbols; when the cyclic prefix is an extended cyclic prefix, one time slot comprises 6 uplink/downlink symbols. As shown in FIG. 2, the subframe of such a frame structure has a configuration characteristic as follows:
Subframe 0 is fixedly used for downlink transmission;
Subframe 1 is a special subframe and comprises 3 special time slots respectively being a DwPTS (Downlink Pilot Time Slot), a GP (Guard Period) and an UpPTS (Uplink Pilot Time Slot), wherein
the DwPTS is used for downlink transmission, the P-SCH is arranged to be sent on the first OFDM symbol of the DwPTS, and the S-SCH is arranged to be sent on the last OFDM symbol of the downlink time slot next to the DwPTS.
the GP is the Guard Period in which no data is transmitted.
the UpPTS is used for uplink transmission and comprises at least 2 uplink SC-FDMA symbols for transmitting the Physical Random Access Channel (PRACH for short).
From the aspects described hereinafter, it can be found that the method for sending the physical broadcast channel in the FDD is already unsuitable for sending the physical broadcast channel in the TDD.
The physical broadcast channel in the TDD requires more capacity than that in the FDD, thus the method for sending the physical broadcast channel in the FDD can not meet the physical broadcast channel capacity requirement in the TDD.
In order to use a synchronization signal for channel estimation in the FDD, the physical broadcast channel is configured to be sent before and after the synchronization signal. The sending positions of the synchronization signal are different due to the difference between the TDD frame structure and the FDD frame structure, thus the sending method in the FDD is unsuitable in the TDD.
The method for sending the physical broadcast channel in the FDD in case of the cyclic prefix being a normal cyclic prefix is different from that in case of the cyclic prefix being an extended cyclic prefix, which also increases the system complexity.
Therefore, it is desirable to design a new method for sending the physical broadcast channel aiming at the TDD frame structure.